The interconnection of microprocessors is a problem which occurs more especially in the use of teleprinters, which comprise several microprocessors. More particularly, the problem posed here is that of interconnecting a master microprocessor and slave microprocessors all connected to a bus over which information must flow from one to the other in series form and at a relatively slow rate.
Heretofore, such interconnection has been made in the following way.
Each information or character transmitted by a master microprocessor for the attention of a slave microprocessor generally comprises an address and the text of the information properly speaking.
Since each micorprocessor is associated with a deserialization and serialization register also connected to the bus, when a master transmits a character, all the registers of the slaves receive this character.
Since each microprocessor is also associated with a recognition interface, which is connected thereto as well as to its deserialization register, the interface, if it recognizes its address in the character received by the associated deserialization register, causes the character to be removed from the register and stored in a buffer register, i.e. a memory, shared between the interface and the microprocessor. If not, the character is rejected from the deserialization register.
If such has been the procedure up to now, it was so that the reception of a character in a slave microprocessor did not cause interruption of its processing then in progress intended to cause it to provide a proper function, such for example as the control of a printer, so that this slave recognized and so accepted and stored this character in its memory. In fact, to accept a character and store it requires in real time a relatively long period, of the order of 100 .mu.s, and a microprocessor does not always have the time required at the moment when the character reaches it, precisley if processing is in progress which cannot be interrupted. With this process therefore, because of the recognition interface, no additional constraint was suffered in real time and the slave microprocessors were thus relieved of the reception of data.
However, the interfaces for recognizing or accepting characters are expensive.
According to another solution, a master microprocessor could be adapted so as to transmit again a character, after receiving one, only after a given period of time, sufficient for a slave microprocessor to be able to finish the processing it has in progress before storing the character. This solution is however not very practical, for the predetermined time in question must be longer than the longest of the processing times which may not be interrupted for the whole of the slave microprocessors.